Mercapto-dihydrocarbyl-triazoles in diffusion transfer process



United States Patent 3,307,944 MERCAPTO-DlHYDROCARBYL-TRIAZOLES IN DIFFUSION TRANSFER PROCESS Edith Weyde, Leverlrusen, Harald von Rintelen, Cologne- Rodenkirchen, and Anita von Konig, Leverkusen, Germany, assignors to Agfa Aktiengesellschaft, Leverkusen, Germany, a corporation of Germany No Drawing. Filed Feb. 20, 1963, Ser. No. 260,038 Claims priority, application Germany, Mar. 10, 1962,

10 Claims. for. 96-29) This invention in general relates to improved direct positive images produced by the silver salt diffusion process and particularly to compounds which influence the colour of the final silver image in the reception layer.

It is already known that the production of an image in the reception layer is advantageously accomplished in the presence of components which influence the colour of the silver precipitated in the reception layer. Such compounds form silver salts difliculty-s-oluble in water and in sodium thiosulphate. Some efficacy is, for example, shown by the compounds described in German Patents No. 473,000 and 890,755.

These compounds have, however, several disadvantages. In particular they retard the formation of the positive image in the silver salt diffusion process, so that longer contact times are necessary. It is, however, desirable to reduce the necessary copying times, and so need exists for compounds which accelerate the diffusion process and the image formation in the positive material and simultaneously produce, as far as possible, a deep black silver image.

We now have found that deep black or bluish black coloured images with reduced processing times are obtained in the reception layer if to the said reception layer and/ or the developer are added mercapt'otriazoles of the following general formula:

wherein R and R represent hydrogen or substituted or unsubstituted alkyl, alkylene, cycle-alkyl or aryl groups.

The mercaptotriazole grouping appears to be responsible for the efficacy of these compounds. The accelerating effect decreases with longer alkyl groups or with aryl radicals. Thus mercaptotriazoles are preferred wherein R or R are alkyl groups or olefinically unsaturated alkyl groups having up to three carbon atoms, such as methyl, ethyl or allyl. The compounds are added in quantities from 1 to 200 mg. per square metre of positive paper and/ or in similar quantities per litre of development solution. Preferred are amounts of 15-50 mg./m. of the reception layer or 15-50 mg./l. of the developer composition The compounds according to the invention are readily soluble in aqueous alkaline mediums and can accordingly be added to developer solutions known in the silver salt diffusion process, without it being necessary to modify the constitution of the developer The compounds are stable in caustic alkali solution. Their effectiveness is 3,307,944 Patented Mar. 7, 1967 only slightly influenced by the development temperature, but development is preferably carried out at temperatures from 15 to 35 C.

The mercaptotn'azlole compounds are known per se and are produced, for example, by the processes described in Beilstein, volume 26, pages 142, 143, 174 and in Journal of the Chemical Society (1959), page 3803. They are generally prepared by the method which will now be described for the case of 3-mercapto-4,5-dimethyl-1,2,4- triazole: 105 g. (1 mol) of 4-methylthiosemicarb azide are introduced into 100 ml. of acetic anhydride and stirred for one hour, then another 25 ml. of acetic anhydride are added. The solution is then boiled under reflux for 5 hours and, after cooling, is diluted with 120 ml. of water. The crude product is purified by recrystallisation from water. Yield: 50 g. (40% of the theoretical) of 3-mercapto-4,5-dimethyl-1,2-triazole. Melting point: 214 C.

Example 1 In a developer of the composition:

G. Anhydrous sodium sulphite 60 Hydroquinone 14 l-Phenyl-3-pyrazolidone 1.2 Caustic soda 11 Potassium bromide 2 ater, 1 litre.

which is in a normal commercial developing apparatus, an unexposed silver chloride negative is developed and brought into contact with a transfer paper which has been coated with a white pigment layer by means of the following solution:

Gelatine g Carboxymethyl cellulose g 23 Colloidal Ag S g 0.06 Sodium thiosulphate g 35 Formalin 30% ml 3 Water, 1 litre.

Example 2 A'reception layer is prepared by applying to a paper g./m. which may perhaps also be baryta-coated, a nucleus layer of the following composition:

Gelatine 20 Colloidal Ag S 0.15

Water, 1 litre.

Above the nucleus layer is cast a sodium alginate layer by applying a 0.75% aqueous solution of sodium alginate which contains mg. of 3-mercapto-4-phenyl-S-methyl- 1,2,4-tri-azole per litre. The layers can contain, in addition, dyestuffs, wetting agents, brightening agents hardeners and other additives.

A negative paper coated with a high-contrast silver chloride emulsion (1.3 g. of Ag./m. is exposed to form the image of a typewritten document and is. brought in known manner, into contact with the reception layer in the presence of the developer (as in Example 1). seconds after leaving the developing apparatus, the two foils are separated one from another and the same negative is developed another 5 times in the same manner, each time with a new positive paper. For the 5th and 6th copies, the contact time between positive and negative is extended to 15 seconds and 30 seconds respectively. In this way, it is possible to obtain from one negative 6 copies of good legibility with greyish black writing.

Example 3 A reception layer is obtained by coating a barytacoated paper with the following solution:

G. Polyvinyl alcohol 16 Sodium alginate 15 Colloidal Ag S 0.05 3-mercapto-4-methyl-1,2,4-triazole 0.035 Sodium thiosulphate 11.5 Borax 0.4

Water, 1 litre.

This material is developed and brought into contact in the usual way with a negative exposed to form an image by the reflex rocess. A contact time of about 5 seconds after leaving the developing apparatus is suflicient to give a black copy of the original with good density.

Example 4 A reception layer is prepared by applying the following solution to a support, e.g., paper (60 g./m.

G. Gelatine 8 Polyvinyl alcohol 2 Propylene glycol ester of alginic acid 40 Colloidal Ag S 0.014 Sodium thiosulphate 55 3-me-rcapto-4-allyl-S-methyl-1,2,4-triazole 0.08

Water, 1.9 litres.

This positive material is processed, in a high speed developing apparatus in the usual way, with a reflexexposed negative directly after leaving the apparatus and a neutral black copy of the original is obtained which has good legibility.

Example 5 A solution of Gelatine g 40 Colloidal Ag S g 0.02 Sodium thi'osulphate g 10 3-mercapto-5-methyl-4-ethyl-1,2,4-triazole g 0.06 Formalin (30%) ml 5 Water, 0.8 litre.

is applied to a film.

After the positive material has been dried, it is given a thin covering with a solution of carboxymethyl cellulose, to prevent adhesion to the negative. After the usual processing with a negative exposed to form an image, and a short contact time, this image-receiving material gives a well-covered and dense transparent copy of the original, which is quite suitable for projection or enlargement.

Similar results are obtained with the following 3-mercaptotriazoles:

1. In the diffusion transfer process by which an imagewise exposed silver halide emulsion is developed in contact with a receiving layer to cause undeveloped silver halide in the emulsion to transfer to the receiving layer and there be converted to a visible image, the improvement according to which the transfer is accelerated and the image tone improved by carrying out the developing in the presence of a 3-mercapto-4,5-dihydrocarbyl-1,2,4- triazole in which the hydrocarbyl groups are alkyl or olefinically unsaturated alkyl having up to 3 carbon atoms, the triazole being present in a concentration of about 15 to 50 milligrams per liter of the developer.

2. The process of claim 1 in which the hydrocarbyl groups are both methyl.

3. The process of claim 1 in which the 4-hydrocarbyl group is methyl and the other hydrocarbyl group ethyl.

4. The process of claim 1 in which the 4-hydrocarby1 group is allyl and the other hydrocarbyl group methyl.

5. The process of claim 1 in which the 4-hydrocarbyl group is allyl and the other hydrocarbyl group ethyl.

6. In the diifusion transfer process by which an imagewise exposed silver halide emulsion is developed in contact with a receiving layer to cause undeveloped silver halide in the emulsion to transfer to the receiving layer and there be converted to a visible image, the improvement according to which the transfer is accelerated and the image tone improved by carrying out the developing in the presence of a 3-mercapto-4,S-dihydrocarbyl-1,2,4- triazole in which the hydrocarbyl groups are alkyl or olefinically unsaturated alkyl having up to 3 carbon atoms, the triazole being present in a concentration of about 15 to 50 milligrams per square meter of the receiving layer.

7. The process of claim 6 in which the hydrocarbyl groups are both methyl.

8. The process of claim 6 in which the 4-hydrocarbyl group is methyl and the other hydrocarbyl group ethyl.

9. The process of claim 6 in which the 4-hydrocarbyl group is allyl and the other hydrocarbyl group methyl.

10. The process of claim 6 in which the 4-hydrocarbyl grou is allyl and the other hydrocarbyl group ethyl.

References Cited by the Examiner UNITED STATES PATENTS 12/1947 Chilton 9650 X 1/1962 Tregillus 9666 X 

1. IN THE DIFFUSION TRANSFER PROCESS BY WHICH AN IMAGEWISE EXPOSED SILVER HALIDE EMULSION IS DEVELOPED IN CONTACT WITH A RECEIVING LAYER TO CAUSE UNDEVELOPED SILVER HALIDE IN THE EMULSION TO TRANSFER TO THE RECEIVING LAYER AND THERE BE CONVERTED TO A VISIBLE IMAGE, THE IMPROVEMENT ACCORDING TO WHICH THE TRANSFER IS ACCELERATED AND THE IMAGE TONE IMPROVED BY CARRYING OUT THE DEVELOPING IN THE PRESENCE OF A 3-MERCAPTO-4,5-DIHYDROCARBYL-1,2,4TRIAZOLE IN WHICH THE HYDROCARBYL GROUPS ARE ALKYL OR OLEFINICALLY UNSATURATED ALKYL HAVING UP TO 3 CARBON ATOMS, THE TRIAZOLE BEING PRESENT IN A CONCENTRATION OF ABOUT 15 TO 50 MILLIGRAMS PER LITER OF THE DEVELOPER. 